Group III-V compound semiconductors such as GaN are widely used in optoelectronics and the like due to wide bandgap, adjustable bandgap, and the like. Such GaN semiconductors are generally grown on a sapphire substrate or a silicon carbide (SiC) substrate. However, these substrates are not suitable for large diameter application and, in particular, the SiC substrate is expensive.
FIG. 1 is a view of a general semiconductor device. Referring to FIG. 1, the semiconductor device includes a substrate 5 and an n-type GaN layer 7.
To address the above-described problems, the silicon substrate 5 that is cheaper than the sapphire substrate or the SiC substrate, easily realizes large diameter and has high thermal conductivity is used. However, lattice mismatch between GaN and silicon is very high and there is a very big difference between coefficients of thermal expansion thereof, and thus, various problems that deteriorate crystallinity, such as melt-back, cracks, pits, surface morphology defects, and the like, may occur. For example, cracks may be caused by tensile strain occurring when the n-type GaN layer 7 grown at high temperature is cooled.
To address these problems, an initial buffer layer (not shown) such as an AlN layer may be formed on the silicon substrate 5. Even in this case, however, pits may be formed due to growth temperature of AlN, lattice mismatch between silicon and AlN, or the like. In particular, an SiN film 9 having a thickness of about 5 Å to about 10 Å may be formed between the AlN initial buffer layer and the silicon substrate 5 and pinholes may be formed in the initial buffer layer.
For these reasons, there is a need to develop a semiconductor device having a structure that does not cause such problems and may provide good characteristics, even when using the silicon substrate 5.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.